of wreckage could unlock clues about why and how the plane had diverted so far off course in one of aviation's most puzzling mysteries. Theories range from a hijacking to sabotage or a possible suicide by one of the pilots, but investigators have not ruled out technical problems.

Australia, China and France have all released satellite images over the past week showing possible debris in the same general area as the latest sighting, but no confirmed wreckage has been located.

PASSENGER RELATIVES DISTRAUGHT

An Australian navy ship returned to the area after being driven away by gale force winds and 20-metre (66 ft) waves on Tuesday, while a Chinese icebreaker and three Chinese navy vessels were now in the search zone.

Two Chinese ships were looking for a two-metre floating object spotted earlier in the day by an aircraft, China's state news agency Xinhua reported.

The United States has sent an undersea Navy drone and a high-tech black box detector which will be fitted to an Australian Defence vessel due in Perth in the coming days.

The so-called black boxes - the cockpit voice recorder and flight data recorder - record what happens during flight, but time is running out to pick up locator beacons that stop about a month after a crash due to limited battery life.

Malaysia said on Tuesday that the U.S. "Towed Pinger Locator" would not arrive in the search area until April 5, which would give it only a few days to find the black box before the beacon battery would be expected to run out.

The prolonged and so far fruitless search and investigation have taken a toll, with dozens of distraught relatives of Chinese passengers clashing with police in Beijing on Tuesday, accusing Malaysia of "delays and deception".

Malaysia's confused initial response to the plane's disappearance and a perception of poor communications have enraged many relatives of the more than 150 Chinese passengers and have strained ties between Beijing and Kuala Lumpur.

Chinese special envoy, Zhang Yesui, met Malaysia's Najib on Wednesday and called for "unremitting efforts" to find the plane, Xinhua said.

MULTINATIONAL INVESTIGATION

Flight MH370 vanished from civilian radar screens less than an hour after taking off and investigators believe someone on the flight may have shut off the plane's communications systems.

Partial military radar tracking showed it turning west and recrossing the Malay Peninsula, apparently under the control of a skilled pilot.